scholarly journals Effect of Heat Treatment on the Microstructure and Phase Composition of ZrB2–MoSi2 Coating

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 779
Author(s):  
Marina Kovaleva ◽  
Igor Goncharov ◽  
Vseslav Novikov ◽  
Maxim Yapryntsev ◽  
Olga Vagina ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Phase Composition ◽  
Lamellar Structure ◽  
Carbon Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mosi2 Coating ◽  
Α Al2o3 ◽  
Sprayed Coating ◽  
Scanning Electron

Composite ZrB2–MoSi2 coating modified by Y2O3 and Al was prepared by a new multi-chamber detonation accelerator (MCDS) on carbon/carbon composites. Postdeposition heat treatment of the samples at 1500 °C for 1 and 6 h was carried out in air. The effect of heat treatment on the microstructure and phase composition of the ZrB2–MoSi2 coating was investigated by scanning electron microscopy and X-ray diffraction phase analysis. The as-sprayed coating presented as a dense lamellar structure, composed of m-ZrO2, t-ZrO2, some hexagonal ZrB2, and cubic Al phases. The m-ZrO2, c-ZrO2, and h-(α-Al2O3) formed at 1500 °C. The coatings after heat treatment (1 and 6 h) exhibited a structure without cracks. The porosity (~1%) of the coating did not change after heat treatment. Thin, continuous, silica-rich film covered the surfaces of ZrO2 and Al2O3 particles, and could have played a role during heat treatment by acting as a grain lubricant for particle rearrangement.

A MoSi2–SiC–Si/MoSi2 COATING TO PROTECT CARBON/CARBON COMPOSITES AGAINST OXIDATION AT 1700°C

2009 ◽  
Vol 16 (03) ◽  
pp. 437-440 ◽  
Author(s):  
QIAN-GANG FU ◽  
HE-JUN LI ◽  
YONG-JIE WANG ◽  
KE-ZHI LI ◽  
HENG WU
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Carbon Composites ◽  
X Ray Diffraction ◽  
Dense Structure ◽  
X Ray ◽  
Slurry Coating ◽  
Mosi2 Coating ◽  
Silicon Sol ◽  
Scanning Electron

In order to protect carbon/carbon ( C / C ) composites from oxidation at 1700°C, a MoSi 2– SiC – Si / MoSi 2 coating was prepared on the surface of these composites by a simple and effective method. The MoSi 2– SiC – Si inner layer was obtained by pack cementation, and the MoSi 2 outer layer was prepared by slurry coating using silicon-sol as the caking agent. The microstructures of the as-prepared coating were examined by X-ray diffraction and scanning electron microscope. Oxidation test shows that, the as-received coating can protect C / C composites from oxidation for more than 107 h at 1700°C in air. The excellent anti-oxidation ability of this coating is attributed to its dense structure and the formation of the SiO 2 film on the coating surface during oxidation.

Effect of Mineralizers on MnNb2O6 Powder Prepared by Hydrothermal Method

2010 ◽  
Vol 156-157 ◽  
pp. 1010-1013
Author(s):  
Yong Ping Pu ◽  
Yong Yong Zhuang ◽  
Kai Chen ◽  
Ning Xu
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Scanning Electron Microscopy ◽  
Particle Size ◽  
Phase Composition ◽  
Hydrothermal Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Highly Dispersed ◽  
Scanning Electron

Pure MnNb2O6 powders was successfully prepared by hydrothermal method using Nb2O5•nH2O and Mn(NO3)2 as precursors and HCl, HF, NaOH, NH4OH solutions as mineralization agent. The phase composition and morphology of the prepared powder were characterized by X-ray diffraction and scanning electron microscopy. The effect of mineralizers on phase formation was investigated. The results show that the MnNb2O6 powders with crystallite size of ~24nm can be obtained with Mn(NO3)2 and Nb2O5•nH2O as precursors in neutral and alkaline solution at 200 for 168h. The particle size of the MnNb2O6 powder was ~300nm after heat treatment at a temperature of 600 . The SEM photographs show that the morphology of the MnNb2O6 powder are rod-like particles and the MnNb2O6 powders are highly dispersed.

Dense ZrB2-MoSi2 Composite Coating Fabricated by a New Multi-Chamber Detonation Accelerator on Carbon/Carbon Composites

2020 ◽  
Vol 987 ◽  
pp. 53-58 ◽  
Author(s):  
Marina G. Kovaleva ◽  
Igor Yu. Goncharov ◽  
Vseslav Yu. Novikov ◽  
Ivan A. Pavlenko ◽  
Maxim N. Yapryntsev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Composition ◽  
Composite Coating ◽  
Lamellar Microstructure ◽  
Carbon Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

A new multi-chamber detonation accelerator (MCDS) was applied to fabricate ZrB2–MoSi2 composite coating containing 20 mol.% of MoSi2 on carbon/carbon composites. Phase composition and microstructure of the coating were characterized by X-ray diffraction and scanning electron microscopy. The ZrB2–20MoSi2 coating displayed compact and lamellar microstructure with porosity lower than 1%, where SiO2 phase was uniformly distributed in the ZrO2 matrix. The coating was well-adhered with carbon/carbon composites. Silica, m-ZrO2, and small amount of Zr(MoO4)2 were formed.

scholarly journals Synthesis and characterization of apatite silicated powders with wet precipitation method

2021 ◽  
Vol 234 ◽  
pp. 00106
Author(s):  
Houda Labjar ◽  
Hassan Chaair
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Analytical Techniques ◽  
Precipitation Method ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wet Precipitation ◽  
Scanning Electron

The synthesis of apatite silicated Ca10(PO4)6-x(SiO4)x(OH)2-x (SiHA) with 0≤x≤2 was investigated using a wet precipitation method followed by heat treatment using calcium carbonate CaCO3 and phosphoric acid H3PO4 and silicon tetraacetate SiC8H20O4 (TEOS) in medium of water ethanol, with three different silicate concentrations. After drying, the samples are ground and then characterized by different analytical techniques like X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning electron Microscopy (SEM) and chemical analysis.

UTILIZATION OF FLY ASH AND CONCRETE RESIDUE IN THE PRODUCTION OF GEOPOLYMER BRICKS

2017 ◽  
Vol 12 (1) ◽  
pp. 63-77 ◽  
Author(s):  
Siriporn Sirikingkaew ◽  
Nuta Supakata
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Compressive Strength ◽  
Phase Composition ◽  
Fly Ash ◽  
Industrial Waste ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

This study presents the development of geopolymer bricks synthetized from industrial waste, including fly ash mixed with concrete residue containing aluminosilicate compound. The above two ingredients are mixed according to five ratios: 100:0, 95:5, 90:10, 85:15, and 80:20. The mixture's physico-mechanical properties, in terms of water absorption and the compressive strength of the geopolymer bricks, are investigated according to the TIS 168-2546 standard. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses are used to investigate the microstructure and the elemental and phase composition of the brick specimens. The results indicate that the combination of fly ash and concrete residue represents a suitable approach to brick production, as required by the TIS 168–2546 standard.

Spark Plasma Sintering of Paper-Derived Ti3AlC2-Based Composites: Influence of Sintering Temperature

2021 ◽  
Vol 1016 ◽  
pp. 1790-1796
Author(s):  
Maxim Syrtanov ◽  
Egor Kashkarov ◽  
Tatyana Murashkina ◽  
Nahum Travitzky
Keyword(s):  
Phase Composition ◽  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Total Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbide Phases ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Scanning Electron

This paper describes the influence of sintering temperature on phase composition and microstructure of paper-derived Ti3AlC2 composites fabricated by spark plasma sintering. The composites were sintered at 100 MPa pressure in the temperature range of 1150-1350 °C. Phase composition and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The multiphase structure was observed in the sintered composites consisting of Ti3AlC2, Ti2AlC, TiC and Al2O3 phases. The decomposition of the Ti3AlC2 phase into Ti2AlC and TiC carbide phases was observed with temperature rise. The total content of Ti3AlC2 and Ti2AlC phases was reduced from 84.5 vol.% (1150 °C) to 69.5 vol.% (1350 °C). The density of composites affected by both the content of TiC phase and changes in porosity.

scholarly journals Standard Hot Pressing as a Possible Solution to Obtain Dense K0.5Na0.5NbO3 Ceramic Doped by Er2O3 and Yb2O3

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4171 ◽  
Author(s):  
Paweł Rutkowski ◽  
Jan Huebner ◽  
Adrian Graboś ◽  
Dariusz Kata ◽  
Dariusz Grzybek ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Rare Earth ◽  
Phase Composition ◽  
Powder Mixture ◽  
Hot Pressing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ultrasonic Methods ◽  
Scanning Electron

In this study, the influence of the addition of rare earth oxides on the phase composition and density of KNN piezoelectric ceramics was investigated. The initial powders of Na2CO3 and K2CO3 were dried at 150 °C for 2 h. Then, a powder mixture for synthesis was prepared by adding a stoichiometric amount of Nb2O5 and 5 and 10 wt % overabundance of Na2CO3. All powders were mixed by ball-milling for 24 h and synthesized at 950 °C. The phase composition of the reaction bed was checked by means of X-ray diffraction (XRD). It had an appearance of tetragonal and monoclinic K0.5Na0.5NbO3 (KNN) phases. Then, 1 and 2 wt % of Er2O3 and Yb2O3, were added to the mixture. Green samples of 25 mm diameter and 3 mm thickness were prepared and sintered by hot pressing at 1000 °C for 2 h under 25 MPa pressure. The final samples were investigated via scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS), XRD, Rietveld, and ultrasonic methods. Phase analysis showed tetragonal and orthorhombic KNN phases, and a contamination of (K2CO3·1.5H2O) was present. The obtained KNN polycrystals had a relative density above 95%. Texturing of the material was confirmed as a result of hot pressing.

Synthesis and Characterization of Y2O3 Nanoflowers

2012 ◽  
Vol 465 ◽  
pp. 76-79 ◽  
Author(s):  
Shuang Zhan ◽  
Xia Li
Keyword(s):  
Fourier Transform ◽  
Phase Composition ◽  
Electron Microscope ◽  
Synthesis And Characterization ◽  
The Novel ◽  
X Ray Diffraction ◽  
Facile Hydrothermal Method ◽  
X Ray ◽  
Scanning Electron

The novel Y2O3 nanoflowers were synthesized through a facile hydrothermal method without using any catalyst or template. The phase composition and the microstructure of as-prepared products were characterized by field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD) as well as Fourier transform infrared spectrum. The formation mechanism for the Y2O3 flowers has been proposed.

Microstructure and Phase Composition of AlN/Al Composite Fabricated by Directed Melt Nitridation

2008 ◽  
Vol 368-372 ◽  
pp. 977-979
Author(s):  
Sheng Li Jin ◽  
Ya Wei Li ◽  
Jing Liu ◽  
Yuan Bing Li ◽  
Lei Zhao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Composition ◽  
Sandwich Structure ◽  
Ceramic Composite ◽  
Growth Direction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Al Composite ◽  
Scanning Electron

AlN/Al ceramic composite was fabricated by directed melt nitridation of pure Al block covered with 10wt% Mg powder at 1300°C in a high purity flowing N2. Microstructure and phase composition of the composite were investigated by scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction. Results showed that AlN is the main phase in the composite and its lattice parameters of a and c are 3.1110Å and 4.9806Å, respectively. The phase composition of the composite changes along the growth direction and a gradient sandwich structure forms. The surface of the composite is made up of a dense and thin nodular AlN layer, underneath which an AlN/Al layer appears, followed by an AlN/Al/MgAl2O4 layer. Thermodynamic calculations predicted the formation of possible phases with the addition of Mg. It suggested that the content of Mg at the reaction frontier of nitridation is considerably lower to 0.15wt% where MgAl2O4 was stable, because of escape and reaction exhaustion of Mg. Once Mg is lower than 0.05wt%, only a dense AlN layer can exist, which prevents the further nitridation of Al melt.

Effect of Synthesis Conditions and Actinide Contents on Phase Composition of Actinide Bearing Ceramics

2003 ◽  
Vol 807 ◽  
Author(s):  
A. G. Ptashkin ◽  
S. V. Stefanovsky ◽  
S. V. Yudintsev ◽  
S. A. Perevalov
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Phase Composition ◽  
Fluorite Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Reducing Conditions ◽  
Dispersive System ◽  
Scanning Electron

ABSTRACTPu-bearing zirconolite and pyrochlore based ceramics were prepared by melting under oxidizing and reducing conditions at 1550 °C. 239Pu content in the samples ranged between ∼10 and ∼50 wt.%. Phase composition of the ceramics and Pu partitioning were studied using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive system (SEM/EDS). Major phases in the samples were found to be the target zirconolite and pyrochlore as well as a cubic fluorite structure oxide. Normally the Pu content in the Pu host phases was 10–12 wt.%. This corresponds to the Pu content recommended for matrices for immobilization of excess weapons plutonium. At higher Pu content (up to 50 wt.%) additional phases, such as a PuO2-based cubic fluorite-structured solid solution, perovskite, and rutile were found.

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